/**
 * 852. 山脉数组的峰顶索引
 * https://leetcode.cn/problems/peak-index-in-a-mountain-array/description/
 */

class Solution {
    public int peakIndexInMountainArray(int[] arr) {
        int n = arr.length;
        int left = 0, right = n - 1;
        while(left < right) {
            int mid = left + (right - left + 1) / 2;
            if(arr[mid] > arr[mid - 1]) left = mid;
            else right = mid - 1;
        }
        return left;
    }
}